The Hidden Dangers of Heat Stress: Long-term Effects on the Kidney, Heart and Brain

The Hidden Dangers of Heat Stress: Long-term Effects on the Kidney, Heart and Brain

According to data published by the World Meteorological Organisation and the Copernicus Climate Change Service, 2023 was one of the hottest years on record in Europe. In the US, periods of extreme heat are projected to double across the lower 48 states by 2100, according to new studies. It is clear that the planet is getting warmer year-on-year with no signs of respite. As a result, heat-related illnesses are becoming far more frequent. 

Heat stress occurs when the body cannot cool itself sufficiently through sweating, increasing core body temperature (CBT). Extreme temperature exposure goes beyond dehydration, heat exhaustion and heat stroke. It’s important to understand the serious long-term effects heat stress can have on the body’s vital organs, particularly when exposure is prolonged or occurs repeatedly. Without adequate cooling, extreme heat can cause significant damage to vital organs, leading to chronic health issues.

Don’t let heat stress be a pain on your kidneys

The kidneys play a crucial role in regulating body fluids, electrolytes and waste products. When the body is exposed to high ambient temperatures, there is an increased risk of dehydration as the body loses fluids through sweating. When fluid intake is insufficient, the kidneys cannot filter blood effectively, leading to a build-up of toxins in the body. This significantly impairs the kidney function, leading to acute kidney injury (AKI) which can lead to chronic kidney disease (CKD) over time. Many studies highlight the strong correlation between rising temperatures and AKI; a study published in the Sage Journal for Workplace Health and Safety found that the incidence of AKI increased by 18% for every 1°C rise in temperature on the same day.

Repeated episodes of AKI can lead to CKD. Research indicates that agricultural workers who are exposed to high temperatures while performing physically demanding tasks are at a greater risk of developing CKD compared to those working in cooler temperatures. CKD is a long-term condition characterised by gradual loss of kidney function. Unfortunately, symptoms go unnoticed and usually become more obvious when it has reached advanced stages. This can happen over months or years and can only be diagnosed through blood and urine tests.

A threat to your heart health

The heart is the hardest working muscle in the human body. On average, it beats around 100,000 times a day, pumping approximately 7,570 litres / 2,000 gallons of blood. Each day, this blood travels around 19,300 kilometres / 12,000 miles through the body, which is more than the (airline) distance from London, UK to Sydney, Australia (16,993 kilometres / 10,559 miles).

The heart is highly sensitive to changes in the body’s core temperature. When the body is exposed to higher temperatures, more strain is placed on the cardiovascular system as it works to maintain a normal body temperature. During heat stress, the body redirects blood flow towards the skin to dissipate heat, reducing blood supply to vital organs. Studies show that, for every 0.5°C that CBT increases, the heart beats an extra ten times a minute. As a result, the heart must work even harder to maintain blood pressure and circulation, which increases the risk of cardiovascular events. 

In severe cases, the risk of a fatal heart attack can double in a heatwave, with heatwaves lasting two days (temperatures ranging from 28°C to 36°C /  82.4°F to 96.8°F) making the risk 18% higher and those lasting four days (34°C to 43°C / 93.2°F to 109.4°F) increasing the risk of a fatal heart attack to 74% higher. While these consequences can be immediate, there are also reports that individuals exposed to extreme heat for extended periods are 20% more likely to develop heart-related complications later in life. Prolonged exposure to high temperatures can lead to chronic cardiovascular issues such as hypertension and ischaemic or coronary heart disease. The constant strain on the heart can cause structural changes, including hypertrophy (thickening of the heart muscle) and fibrosis (scarring of heart tissue).

How heat affects the brain

The brain is another vital organ in the human body that is susceptible to both short- and long-term effects of heat stress. In order for the brain to function efficiently and effectively, it relies on a stable temperature. When the body overheats, at 40°C / 104°F, the blood-brain barrier begins to deteriorate. This barrier separates the brain tissue from the bloodstream, keeping out unwanted particles and bacteria but allowing in the oxygen and nutrients the brain needs. At high temperatures, unwanted proteins and ions can build up in the brain, often causing an inflammatory response and negatively affecting its normal function.

Studies have shown that even mild heat stress can impair cognitive function, leading to difficulties with concentration, memory and decision-making, while lack of oxygen to the brain causes fainting, which is one of the most common side effects of heat stroke. Severe heat stroke can result in brain damage due to swelling and increased intracranial pressure. Between 10% and 28% of heat stroke survivors experience persistent brain damage.

Prolonged or chronic exposure to extreme heat can contribute to and increase the risk of neurodegenerative diseases such as dementia and Alzheimer’s. While exact mechanisms behind this are still being reviewed, some theories suggest that heat stress may damage brain cells or accelerate the degeneration of neural pathways. There is also growing concern about the potential link between heat stress and an increased risk of stroke. Heatstroke can directly damage brain tissue and lead to long-term neurological complications.

Additionally, sleep quality can be significantly affected by hot temperatures. Disrupted sleep can further exacerbate cognitive decline and increase the risk of mental health issues such as anxiety and depression. A US study of mental health-related emergency department visits found an 8% increase in mental health visits on the hottest days of summer compared with the coolest days.

What are some prevention and mitigation strategies for heat stress?

Understanding the long-term implications of heat stress on the body’s vital organs and functions highlights the need for effective prevention strategies. While summer can be the season where more people are exposed to the risks, several occupations require operations in high temperatures all year round. Organisations that employ workers in such environments must understand the long-term effects of heat stress and take the necessary steps to keep workers safe. Here are some key measures.

Wearable solutions

Organisations are unable to help prevent incidents if they do not have access to the right information. Implementing a wearable solution like Bodytrak® captures real-time actionable insights to help both workers and organisations prevent the early onset of heat stress. By measuring and monitoring a user’s CBT in real-time, users and supervisors can be alerted if an individual’s CBT is beginning to reach levels that could put them at risk. This individualised approach ensures that the information is correct and intervention can be actioned immediately, reducing any long-term consequences.


Staying well hydrated is crucial in preventing kidney damage and supporting cardiovascular function during heat exposure. Regular fluid intake helps maintain blood volume and electrolyte balance.

On average, drinking at least eight to ten glasses of water a day is recommended; however, in hot conditions and during physical exertion, intake should increase. According to the Centers for Disease Control and Prevention, when working in higher temperatures, workers should consume 1 cup (8 ounces / 250mls) of water every 15–20 minutes. Drinking at shorter intervals is more effective than drinking large amounts frequently. Even if workers replenish lost sweat with equal amounts of water, they may still be dehydrated due to lost salt from the body. This is when fluids such as sports drinks that contain salts may be more effective.

Heat acclimatisation

Heat acclimatisation is the improvement of our body’s tolerance to heat which develops gradually by increasing exposure to an environment or duration of tasks performed under those conditions.

Gradually increasing exposure to hot conditions can help the body adapt, improving heat tolerance and reducing the risk of heat-related illnesses. Starting with short periods of heat exposure, and gradually increasing the duration and physical exertion, improves the body’s ability to control CBT.

Cooling strategies

Implementing cooling methods, such as wearing light clothing, seeking shade, taking breaks in air-conditioned areas and removing any personal protective equipment when taking time out, can significantly reduce the risk of heat stress.

Portable cooling devices, like handheld fans or cooling towels, can be particularly effective for outdoor activities.

Monitoring vulnerable populations

There are a number of factors that can increase the risk of heat-related illnesses, such as elderly individuals, young children, and those with pre-existing health conditions. Monitoring and providing additional support to these groups, whether that be through wearable solutions or checking in during heatwaves, can reduce their susceptibility to heat stress.


As global temperatures rise and heatwaves become more frequent, understanding the long-term effects of heat stress on the body’s vital organs has never been more critical.

Heat stress poses a significant threat to the kidneys, heart and brain, with long-term exposure leading to chronic health conditions and increased mortality risk. By understanding these impacts and implementing effective prevention strategies, we can mitigate the risks and protect the health and well-being of loved ones and workers alike. It is essential to stay informed and hydrated and take proactive action to safeguard the well-being of all in the face of increasing temperatures in the workplace and beyond.

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